Mixing nostalgia, baseball and a boy's mostly epistolary friendship with a 1940s baseball star, this inventive but sentimental novel consists entirely of letters, fictional newspaper clippings, telegrams, war dispatches, report cards and other documentary fragments. Growing up Jewish in a tough, Italian Brooklyn neighborhood, Joey Margolis is troubled by anti-Semitic neighbors, by Hitler's rising power, by his parents' divorce and by his absent cad of a father. Craving a surrogate dad, Joey strikes up a correspondence with Wisconsin-born New York Giants slugger Charlie Banks. The boy's outrageous fibs, tough-guy posturing and desperate pleas grab the reluctant attention of the superstar, whose racy vernacular guy-talk (peppered with amusing misspellings and misusages) hints at his deepening affection for Joey. Charlie is a politically enlightened proletarian ballplayer with a heart of gold. His liberal views find an echo in Joey, whose best friend, Japanese-American Craig Nakamura, gets shipped off with his family to a wartime internment camp. In a plot that swerves from Joey's Bar Mitzvah to a White House meeting with President Roosevelt to a tearjerking climax, Kluger keeps changing the pace and piles on a slew of period references with a heavy hand. Despite these flaws, this debut novel is at its best a poignant, golden evocation of one boy's lost innocence. Author tour. (June)